Treatment of fibrous material



Patented Nov. 27, 1934 UNITED STATES PATENT OFFICE 7 TREATMENT OFFIBROUS MATERIAL No Drawing. Application April 7, 1930, Serial No.442,464

8 Claims. (01. 18-50) This invention relates to processes for theproduction of combinations of rubber and fibrous materials such as woodpulp, hemp, cotton, leather, asbestos and other fibres of animal,vegetable or mineral origin and particularly to such combinations wherethe rubber is in the form of a dispersion or emulsion either naturallyoccurring or artificially prepared. The present method is also concernedwith an improved method for 10 combining rubber and fibres of any sort.

The principal object of the invention is to Drepare a plastic materialfrom natural or artificial dispersions of rubber and fibres which can beformed into sheets without the use of ordina y paper making machinerysuch-as the so-called Fourdrinier machine, cylinder machines and wetmachines but to substitute for these machines calenders or other devicesfor obtaining relatively thin sheets, and tubing machines, pug mills andmolding devices for forming the plastic material into continuous ribbonsof anydesired shape, or

molded article such as valves or cups for pumps,

shims for use in the automotive industry, soles and heels for theleather shoe industry and the like.

The invention also includes among its objects the preparation of fibreand rubber combinations by combining latex, either natural orartificially prepared with fibres of any desired length, as

such,.0r fibres that have been hydrated to any degree in an ordinarybeating engine and also fibres very much longer than can be handled withthe usual paper making equipment and approaching the ordinary length ofnaturally oocurring fibrous materials such as cotton, asbestos,

etc.

The invention comprises mixing fibrous materials in any type of mixingapparatus such as a Werner and Pfieiderer mixer or the like with eithernatural or artificially prepared latex in the presence of addedprotective colloids which tend to stabilizethe latex and to permit ofsevere mechanical and heat treatment without coagulation of the rubber.In some cases the protective colloids may not be necessary. The fibresused f r the mixture may be either specially prepared by beating in anordinary beating engine to any desired degree or may be separated intheir dry condition by carding, picking or shredding by 0 means of anysuitable type of impact grinder or shredding machine and may be fed tothe mixing apparatus in either a moistened or dry condition. The type ofprotective colloid where it is used in the process of this inventiondepends to a large extent on the end product which is desired and theextent of the mechanical and heat treatment to which the mass is to besubjected during the process and the degree of plasticity required inthe resulting mass to permit of sufficient sheeting or molding. Ingeneral, there may be added proteins such as glue, casein, vegetable andanimal albumens, or a mixture of the proteinous constituents of blood,modified albumens such as protalbinic and lysalbinic acids, protectivecolloids derived from vegetable sources such as starches, either in thenaturally occurring or modified form, such as acetylated starches,saponin and the like, also protective colloids derived from in organicsources such as silicic acid and the freshly precipitated hydroxides ofiron and aluminum and the colloidal silicates of iron, aluminum,magnesium, etc., also the soluble or partially soluble compounds ofsaponifiable organic acids such as oleic, stearic, palmitic, as such, orin the form of natural oils or fats, the resin acids and the like, orany suitable mixtures of the foregoing. It has also been foundadvantageous in order to promote the mixing of the fibrous materialswith the latex and particularly where relatively long fibres are used,to use wetting agents common to the industry such as the sulphonatedoils, triethanolamine, sulphonated diphenyl, either as such .or incombination with alkalies or the above mentioned protective colloids.

Heretofore it has been proposed to make combinations of fibrousmaterials with either natural or artificially prepared latex byincorporating the latex and fibrous ,pulpwith or without the addition ofprotective colloids in an ordinary paper making beating engine and thento add coagulants in such form as to precipitate the rubber upon thefibres and cause the substantially complete separation of the aqueousportion of the latex from the rubber and the latex.

The preferred method of carrying out the invention is as follows:

The fibrous material such as cotton is placed in a beating engine withwater in the usual way and beaten to the desired condition. The beatenfibre is then removed from the beater by any suitable means and placedin a drainer so as to remove the excess water. Any further quantity ofwater may, if desired, be removed by centrifuging in any of the standardtype basket centrifuges or by pressing at low pressures between theplatens of a mechanical or-hydraulic press or by any other suitablemethod. The removal of the water may also be accomplished by running thepulp over a so-called wet machine where the'resulting sheet built up onthe pick-up 1 or making roll will contain from to 70% moisture and thissheet may be further dehydrated by pressing as above. Enough moistureshould be retained in the sheet to permit ready breaking up of thefibres in the mixer. The wet mass resulting from this operation may thenbe placed in a W & P mixer or any suitable type of mixing or kneadingmachine or it may be placed in a Banbury mixer, well known in the rubberindustry, or in any special type of beating engine designed to handlepulp of high fibre content. After the wet mass of fibre has beendisintegrated in the above mentioned mixing or kneading machine, alkali,preferably in concentrated solution so as not to unduly increase thewater content of the fibrous mass, may be added to aid in preserving thestability of the later added dispersion of rubber. Any alkali such asammonia, caustic soda or caustic potash may be used. The resultingmixture should have an alkalinity corresponding to pH 8 to pH 12 andpreferably between pH 10 and pH 12. Any of the above mentionedprotective colloids may then be added to the mass in the mixer or may beadded to the latex before it has been added to the mixer. The amount ofprotective colloid required depends on the nature of the fibre used, thenature of the protective colloid itself and the properties desired inthe finished product. If animal glue is used as the protective colloidand the desired finished product is to be flexible, the proportion ofglue on the weight of the finished batch should be between the limits ofapproximately 5 and approximately 15% depending on the grade of glueused, it being recognized that the higher grades of glue are moreflexible than the cheap- 61' grades. After the protective colloid hasbeen added to the mass in the mixer the latex is added in a proportionto give the desired rubber content in the finished product. As statedabove the protective colloid may be mixed with the latex before placingin the mixing machine. Either before or after the latex is added anydesired compounding materials may be added such as pigments to givecolor, stiffness, or density to the finished product, or softeners togive plasticity or moldability either to the mass before sheeting ormolding or in the finished product. The materials should be thoroughlymixed. The softeners may be of two classes-first, softeners such asglycerine, triethanolamine, diethylene glycol which tend to soften andrender more flexible the glue used as protective colloid, and sec- 0nd,softeners such as asphalt, oils, pine tar,

pitches, waxes and the like which have a softening action on the rubbercontained in the mixture. If it is desired to have the finished productwaterproof, compounding materials of the heavy metal soap type such asaluminum stearate, oleate, palmitate and resinate may be added. Alsosome of the above mentioned rubber softeners such as asphalt have beenfound to be beneficial in this condition.

The mixing or agitation is carried on for a sufficient length of time togive a uniform mixing of all the ingredients. Owing to the fact that anappreciable amount of water has been added to the batch with theaddition of the protective colloid and the latex, the mass at this stagewould have a comparatively high fluidity and if passed between the rollsof a calender for sheeting or through a tubing machine or other moldingdevice an appreciable amount of water would separate from the mass,carrying with it a portion of the protective colloid and latex and otheradded materials desired in the finished product. In order to increasethe viscosity of the mass and to prevent separation of water and theconsequent loss of the desired compounding ingredients, it is preferredto thicken the mass to a stage where it has a dough or putty-likeconsistency and can be calendered into a smooth and homogeneous sheet ortubed and molded into various shapes. The viscosity of the mass may beincreased to the desired point in one of several general ways dependingon the nature and amount of protective colloid used. In the case of theglue used in the above example, increase in viscosity or thickening mayif desired be brought about by the evaporation of part of the water inthe mixture by means of applying heat in any desired manner to themixing apparatus. The application of heat, however, is less preferred onaccount of its depolymerizing and coagulating effect on the rubbercontained in the batch and also because ordinary protective colloids,particularly of the proteinous type, coagulate at relatively lowtemperature. For example, most proteins can be coagulated from solutionon simply heating to approximately 65 C. The use of temperatures belowthis necessitates extremely long periods of time to carry out therequired evaporation. In lieu of heat, or with the use of only a slightamount of heat evaporation, it is preferred to increase the viscosity bychemical means such as the addition of gel-forming agents of theinorganic type or the formation of these gel-forming agents in situ. Theaddition of from about 2 to about 8% of silicic acid formed in situ byadding a solution of sodium silicate and boric acid to the mixture hasbeen found to give thickened masses which may be readily formed intosheets by calenders or any other shapes by tubing or molding. Thefreshly precipitated hydroxide of aluminum and iron have also been foundeffective in this connection. These gelforming agents may be used withor without the use of the other protective colloids.

Another method of thickening the mass or obtaining gel formation withoutthe evaporation of appreciable amounts of the water used in preparingthemixture involves the use of protein precipitants or gelling agents, suchas formaldehyde, polyhydric phenols, organic color bases and suchinorganic compounds as ferric chloride and acetate, mercuric chloride,basic lead acetate, basic aluminum acetate, phospho tungstic acid. Ithas also been found that the use of zinc acetate and in some cases zincoxide in finely divided condition promotes the formation of gelscontaining comparatively large amounts of water when used in connectionwith proteinous protective colloids. These protein-precipitating gellingagents, if desired, may be used in connection with any of the abovementioned processes. It is necessary to use considerable care in addingthese protein-precipitating gelling agents, since under ordinarycircumstances they would cause precipitation or coagulation of theprotective colloid and rubber from the latex. However, by adding themvery slowly, thoroughly mixing each portion before the addition of moreof the agent, it has been found that a very definite thickening actionresults and that the mass in the mixer attains the consistency of heavydough or putty which can be easily calendered in sheet form or molded asdescribed above. It has also been found advantageous to heat the mass inthe mixer to a temperature not exceeding 45 to 50 C. in order to promotethe thickening action of the above agents. As stated above, however,care must be taken not to carry the temperature appreciably above 50 C.because there is danger of irreversibly coagulating both the protectivecolloid and the rubber.

The plasticmass resulting from the above procedure may be of almost anyviscosity desired ranging from a material which will easily flow and maybe spread out by means of rollers or knives on endless metallic belts,screens and the like to form sheets which may be subsequently dried andfinished by calendering or pressing, if desired, to products with a veryhigh viscosity which are well adapted to forming into sheets by means ofcalendering or tubing or forming into ribbons or other shapes by meansof the ordinary tubers of the rubber industry or pug mills such as areused in the ceramic industry, or can be formed into any desired shape byspecially constructed mold. Thus the thickened mass may be shaped intoany desired form, as by a sheeting, calendering, tubing, or moldingoperation or the like, and dried to the final product. The productsresulting from this process are different from those obtained'by theordinary milling of compounding materials and crude rubber because it ispossible to incorporate much higher percentages of fibrous materials inthe compound and to use fibres of much greater length than it ispossible to accomplish by the regulation milling operation. Also theeffect of the various compounding ingredients used together with thevulcanizing agents is much more pronounced in these compounds becausethe process gives a much more uniform distribution and dispersion ofthese compounds throughout the mass.

While the invention has been described with particularity by way ofillustration it is not intended so to limit the invention inasmuch asmany variations in the details thereof may be made without departingfrom the principles and spirit of this invention, the scope of which isset forth in the following claims.

Having thus described our invention, what we claim and desire to protectby Letters Patent is:

l. A process for the manufacture of fibre and rubber combinations formolding, sheeting, tubing and like operations which comprisesintroducing an aqueous dispersion of rubber and fibrous material into amixer and uniformly mixing the same, and evaporating water from the sameto thicken the mixture without substantial coagulation of the rubbertherein.

2. A process for the manufacture of fibre and rubber combinations formolding, sheeting, tubing and like operations which comprisesintroducing an aqueous dispersion of rubber and fibrous material into amixer and uniformly mixing the same, and thickening the mixture by theaddition of an inorganic gelling agent without substantial coagulationof the rubber therein.

3. A process for the manufacture of fibre and rubber combinations formolding, sheeting, tubing and like operations which comprisesintroducing an aqueous dispersion of rubber and fibrous material into amixer and uniformly mixing the same, and thickening the mixture by theaddition of an inorganic gelling agent and evaporation of water from themixture without sub stantial coagulation of the rubber therein.

4. A process for the manufacture of fibre and rubber combinations formolding, sheeting, tubing and like operations which comprisesintroducing an aqueous dispersion of rubber and fibrous material into amixer and uniformly mixing the same, and thickening the mixture withtheaid of chemical means and heat evaporation without substantialcoagulation of the rubber therein.

5. A process for the manufacture of fibre and rubber combinations formolding, sheeting, tubing and like operations which comprisesintroducing an aqueous dispersion of rubber, fibrous material, and aprotective colloid into a mixer and uniformly mixing the same, andthickening the mixture by the addition ofv an inorganic gelling agentwithout substantial coagulation of the rubber therein.

6. A process for the manufacture of fibre and rubber combinations formolding, sheeting, tubing and like operations which comprisesintroducing an aqueous dispersion of rubber, fibrous material, and aprotective colloid into a mixer and uniformly mixing the same, andthickening the mixture by evaporating water from the same withoutsubstantial coagulation of the rubber therein.

7. A process for the manufacture of fibre and rubber combinations formolding, sheeting, tubing and like operations which comprisesintroducing an aqueous dispersion of rubber, fibrous material, andprotein material into a mixer and uniformly mixing the same, andthickening the mixture with the aid of chemical means and heatevaporation without substantial coagulation of the rubber therein.

8. A process for the manufacture of fibre and rubber combinations formolding, sheeting, tubing and like operations which comprisesintroducing an aqueous dispersion of rubber, fibrous material, andprotein material into a mixer and uniformly mixing the same, andthickeningthe mixture by the addition of an inorganic gelling agent andevaporation of water from the mixture without substantial coagulation ofthe rubber therein.

REED P. ROSE. ALLEN F. OWEN.

